Extraction-absorptiometric determination of palladium (II) with bismuthiol II
1973 Volume 22 Issue 3 Pages 264-269
Details
1973 Volume 22 Issue 3 Pages 264-269
The writers found, that the reddish brown palladium-bismuthiol II complex can be extracted into certain organic solvents and an absorptiometric method for the determination of small amounts of palladium in conjunction with extraction of the complex is possible.
The extraction of the complex from hydrochloric, sulfuric, nitric, phosphoric, and perchloric acid has been investigated and that from 0.5 to 1.0N perchloric acid with tributyl phosphate has been found to give the most stable color.
The complex could be quantitatively extracted by tributyl phosphate from perchloric acid solution of an acidity ranging from 0.5 to 1.0N but it could not be extracted with the same solvent from alkali solution. The molar extinction coefficient of the complex in tributyl phosphate at 450 nm was 4.60 × 103, and the sensitivity according to Sandell's expression was 0.023 μg/cm2. Beer's law was obeyed up to 15 μg/ml of palladium for the absorbance measured at 450 nm. It was confirmed, by the method of continuous variations, that the ratio of palladium to bismuthiol II in the complex in tributyl phosphate was 1 to 2.
On the basis of these observations, the writers propose the following procedure :
A 50 ml aqueous solution which contains up to 150 μg of palladium and 0.75N perchloric acid is prepared. It is shaken vigorously for 90 sec with 10 ml of 0.05% tributyl phosphate solution of bismuthiol II and the absorbance of the extract is measured at 450 nm.
Though copper (II), bismuth (III), iron (III), osmium (VIII), selenium (IV) etc. interfere with the determination of palladium, the interference except with the last two can be eliminated if the organic phase is washed with 50 ml of sodium hydroxide (about 0.16 N) after the extraction.
The osmium-bismuthiol II complex which is green in both acid and alkali media can be extracted with tributyl phosphate. Since the complex in tributyl phosphate has an absorption maximum at about 780 nm under the conditions employed for the determination of palladium, palladium and osmium can be determined simultaneously by extracting their bismuthiol II complexes with tributyl phosphate.
